Heating apparatus



Aug. 1, 1944. J. P. WALKER IEFAL HEATING APPARATUS- Filed April '7, 19412 Sheets$heet 1 JayRWalker 622mm: 4 dkuyaw JNVENTOR ATTORNEY Aug. 1,1944.v J. P. WALKER ETAL HEATING APPARATUS Filed April 7, 1941 2Sheets-Sheet 2 W I R mm% Y Q B 6 Patented Aug. 1,1944

2,354,932 HEATING APPARATUS Jay P. Walker and Clarence 0. Glasgow,Tulsa, Okla., assignors to National Tank Company,

Tulsa, Okla.,

a corporation of Nevada Application April 7, 1941, Serial No. 387,276

17 Claims; (Cl. 621) This invention relates to gases and liquids, andparticularly to indirect heaters of the type employing a liquid heattransfer medium for conveying heat from a heat-supplying element to aheat-absorbing element, both of which are submerged in said medium.

Heaters of the type herein contemplated are useful particularly for theheating of various fluids such as oil, gas, water and the like tovarious temperatures. at high or low pressures, and at a relatively highheat transfer efficiency.

In the production and handling of oil and gas, particularly, heating ofthese fluids is often required for a variety of purposes. In the case ofoil, such purposes may include removal of suspended and emulsifiedwater, reduction in viscosity, prevention of paraflin precipitation,etc., and in the case of gases,.particularly high pressuremoisture-containing gases, heating of the gas is often required forpreventing the formation of solid hydrocarbon hydrates in the containingpipes and vessels, dueto the low temperatures resulting from thereduction in pressure from high to low pressures.

In many of the more conventional heaters heretofore employed for theseand kindred purposes, local over-heating and corrosion of the tubes,tanks, etc.,'in whichthe fluids are contained. often result from thedirect application thereto of flames and high temperature combustiongases used for heating the fluids. In other cases, the heaters arerelatively inefficient heat transfer devices and are, therefore,relatively expensive to construct and operate.

It is, therefore, a primary object of this invention to provide arelatively simple and efficient heater for heating the aforementionedfluids in a manner to avoid the various diiliculties commonlyencountered with more conventional heaters.

It is an important object of this invention to provide a heater of thetype employing a liquid heat transfer medium and having novel featuresof construction whereby circulation of the medium is effectedthermo-syphonically at comparatively high velocity and heat transferemciencies throughout the heater.

Another important object of this invention is the provision of a heaterof the character described which is particularlyadapted for heating highpressure gases while they are undergoing expansion to lower pressures toprevent formation of hydrates.

Other and more specific objects and advantages of this invention willbecome apparent from the following detailed description when read inconjunction with the accompanying apparatus for heating illustrate aheater in accordance with one embodiment of this invention' It will beunderstood, however, that this invention is not limited to anyparticular form of apparatus, but that various changes may be made indetails but within the scope of the appended claims, without departingfrom the spirit of this invention.

In the drawings:

Fig. 1 is a longitudinal sectional view of a heater in accordance withone embodiment of this invention,

Figs. 2 and 3 are opposite end elevations thereof,

Fig. 4 is a top view of the heater of Fig. 1,

Fig. 5 is a cross-section taken along line 5--5 of Fig. 1, and

Fig. 6 is an enlarged fragmentary view of a detail of the apparatus.

Referring to the drawings, the heating device there illustrated includesan elongated cylindrical shell or tank I, preferably horizontallypositioned on suitable spaced support members 2-2. At one end the tank Iis provided with an enlarged flanged manway 3 communicating with thelower portion of the tank, and at the opposite end with a secondenlarged manway 4 communicating with the upper portion of the tank. Thetop of the tank is provided with a small vapor dome 5, into which isconnected a more or less conventional type of combination pressure andvacuum relief valve 6. A valved filling and pumpout connection I isprovided in the bottom of the tank.

A partitioning member, designated generally by the numeral 8, extendslongitudinally and transversely through the interior of tank I and makessubstantially liquid-tight connection along its side edges with the sidewalls of the tank. The partitioning member thus divides the tank intoupper and lower compartments 9 and I0, respectively, and itslongitudinal dimension is made less than that of the tank, whereby theends of the partitioning member may be spaced from the adjacent ends ofthe tank to thereby provide longitudinally spaced, upright passagewaysII and I2, respectively, providing communication between thecompartments at the opposite ends thereof.

drawings, which In the form shown in the drawings, partitioning member 8is constructed of spaced parallel metal plates I3--l3, separated byangle irons "-44, which also serve to close the ends of the member.Since, as previously noted, the side edges of member 8 make liquid-tightconnection with the side walls of the tank, and the ends are closed, asnoted, by angles "-44, the space between the plates becomessubstantially a dead air space which is thermally non-conducting, afeature which contributes importantly to the efilcient functioning ofthe device, in preventing substantial transfer of heat directly from onecompartment to the other through the partition. Instead of employing apartitioning member having a dead air space of the form described, itwill be evident that a partitioning member constructed of any suitablethermally non-conducting material may be substituted therefor withsimilar advantages.

Attached to one end of partition member 8 is a baffle plate II whichextends vertically into compartment 3 to a point spaced from the top oftank I and transversely thereof into substantially fluid-tightengagement with the sides of the tank. A similar bailie plate I! issimilarly attached to and to the sides of the tank, but extendsdownwardly into compartment III to a point spaced from the bottom of thetank. Plates I5 and I8 operate to further define said passageways I Iand i2 and function as weirs to restrict the inlet and outlet areas ofthese passageways.

Manway 3 is provided with a removable cover plate I I in which ismounted an elongated heating 'unit, designated generally by the numeralll. The heating unit I I comprises an elongated cylindrical fire tube IIwhich is adapted to be inserted longitudinally into compartment Iiithrough manway 3 to a point adjacent but spaced from baile plate II. Theinner end of fire tube I 3 is closed by a head 20, and a pair offlue-gas ducts 2l2l connect into opposite sides of fire tube ll adjacentits inner end, return generally parallel to the fire tube throughcompartment II, and emerge through cover plate ll to discharge into asmoke box 22 which surrounds the outer end of the fire tube. A smokestack 23 communicates with the top of the fire box. A fuel supply pipe24, provided with a fuel control valve 25, extends into the outer end offire tube II and connects to a burner head 26, which is so positioned inthe fire tube as to direct flames and hot gases of combustion generatedthereby through the fire tube, the gases of combustion then passingthrough ducts 2|2l to smokebox 22 and thence to stack 23. By mountingthe entire heating unit II in cover plate H, which is adapted to bebolted or otherwise conventionally the opposite end of the partitioningmember 8 v connected to manway 3, the entire unit is readily 1removable, if desired, for repair or replacement or for shipment as aseparate portion of the heater assembly.

Manway I is also provided with a removable cover plate 23 in which ismounted one end of a heat-extracting unit. designated generally by thenumeral 21. The unit 21 comprises an elongated tubular coil 23consisting of a plurality of connected tubing runs, and having an inlettube 29 and an outlet tube 33 which extend through cover plate 2 to theexterior thereof. The remainder of coils 23 is adapted to be insertedlongitudinally into compartment 9 through manway I to a point adjacentbailie plate I 5. The tubes comprising coil 23- extend through aplurality of transverse tube sheets or gitudinally or the tank whichprovide support for the tubes and serve also as bailles to divide thecoils into a plurality of sections. The coil 28 is spaced verticallyfrom partitioning member 8 by resting the supports 3| on transverselyspaced angle iron rails 32-32 which extend longitudinally on the uppersurface of member 8. In passing through cover plate 23, inlet tube 29and outsupports 3|, spaced lonlet tube 30 pass through stuillng boxes 33and 34, respectively, to allow for removal of the cover plate from thetubes. Since the coil 28 is firmly held only at one end, namely, in thecover plate, it is free to move longitudinally with the thermalexpansion and contraction thereof, the supports sliding on the rails 32.By mounting the heatextracting unit 21 in the cover plate 23, which isadapted to be bolted or otherwise conventionally fastened by manway l,the entire unit is removable bodily for repair or replacement orseparate shipment, as may be desired.

Inlet tube 29 is provided with a pipe connection 35 through which afluid to be heated may be supplied to the coil, and may also be providedwith a valve, designated generally by the numeral 38, for purposes to bemore fully described hereinafter. Outlet tube 30 is also provided with apipe connection 31 for conveying the fluid heated in coil 28 to asuitable point of disposal (not shown). Connection 3! is ordinarilyprovided with a thermometer well 33 through which temperatures of theemerging fluid may be obtained when desired. A thermometer well 39 isalso provided in the outlet end of tank i to enable the taking oftemperatures of liquids within the tank.

The entire tank is filled with a suitable liquid heat transfer medium,designated by the numeral 40. This material is supplied to the tank andwithdrawn also, if desired, through valved connection 1. The liquid heattransfer medium 40 may be any liquid suitable for transferring heat fromheating unit It to heat-extracting unit 21, and is preferably one whichremains in liquid state at the particular temperature and pressureemployed in the device. Water is a cheap and convenient medium for usewhen temperatures below about F. are employed, but it will be understoodthat this invention is not to be restricted to the use of water as theliquid heat transfer medium, since it will be readily appreciated thatthere are many liquids which are known to have suitable physical andchemical characteristics for this purpose.

The above-described apparatus is employed in the heating of a fluid inthe following manner:

Assuming that the liquid is one which is to be heated to sometemperature below the boiling point of water, the tank I is filledsubstantially completely with water and relief valve 6 is set to hold apressure of one pound or so on the tank. The fluid to be heated issupplied from a suitable source through pipe 35 to the inlet of the coil28 and circulated through the coil to the discharge connection 31 whichconveys it to the desired point of disposal. Fuel is supplied throughpipe 24 under the control of valve 25 to the burner 23 and burned in theentrance of fire tube IS. The resulting flames and hot gases ofcombustion then flow through the fire tube and return through ducts2|-2l to the stack 23, being aided by the draft normally created instack 23. The flames and hot gases passing through the heating unit,heat the surfaces of the latter which transfer the heat to the adjacentliquid medium 40. The heated liquid rises, due to its decreased densityand is displaced by the .colder and consequently heavier liq'uidentering compartment ill from passageway l2. The heated liquid is forcedto flow beneath partitioning member 8 into passageway ll. Since member 8limits the extent of the rise of heated liquid, a more rapid movement ofthe liquid results in the direction of passageway ll. Here baffle plateIt forces the liquid to rise to the top of the baffle and flow throughthe relatively restricted inlet provided between the top of the bailleand the top of the tank, thereby further increasing its velocity. Alsoby forcing the liquid to rise to the top of the baffle l5, ated foradditionally increasing the velocity of the liquid. The heated liquidthen strikes the relatively cooler coil 20 which absorbs heat from theliquid and transfers it to the fluid passing through the interior of thecoil to heat the latter. As the transfer liquid continues its flow backtoward passageway l2, more heat is continuously extracted from it and as'it loses heat, the liquid increases in density and sinks to the uppersurface of member 8 along which itis forced to flow to passageway l2,and thence back to compartment l thereby completing the thermo-syphoniccycle initiated by the heating in compartment l0. tion of flow of theheated liquid is generally counter-current to approximately half of theflow. through for that reason, is additionally eflicient in transferringheat. The provision of the relatively non-conducting partitioning member8 prevents dissipation upwardly over anextended area of the energy ofthe heated transfer liquid, and this feature together with therestrictive effect of batlles l and I8 forces the liquid to flow along acomparatively confined path and thereby produces relatively highvelocity thermo-syphonic flow, which in turn results in high heattransfer rates between the carrier liquid and the heat extracting unit.

The supports 3i, being upright and extending transversely of the tank,immediately above the rails 32, not only provide barriers to thethermosyphonic flow of the heated transfer liquid, but serve to divertsuch flow This arrangement also not only divides the downward flow, butit causes the liquid to flow, more or less, transversely of the coiltubes which promotes the over-all heat transfer efliciency. It furtherelongates the -travel path and tends to, more or less, automaticallyproportion the flow of the liquid in accordanc with the mean temperaturedifferences between the heated transfer liquid and the segments of thecoil defined by the supports 3|. Obviously, the relatively broadlongitudinal flow space along the upper side of the partition 8 andunder the supports 3|, provides a relatively cool zone which has itsmanifest beneficial results.

It will be understood that the heating device described above may beemployed for heating various fluids to any desired temperatures underany desired pressures. The temperature employed determines the boilingpoint characteristics of the heat-transfer medium. In order to obtainmaximum efliciency, the transfer medium should be retained in liquidcondition throughout the heat transferring operation. Ordinarily thepressures applied to the transfer liquid are nominal pressures when thetemperatures are below the normal boiling points of these liquids, or ahigher pressure sufficient to prevent vaporization of these liquids,when their normal boiling temperatures are exceeded, may be employed.

Where water is used as the transfer medium, it is ordinarily employedwhere temperatures up to about 190 F. are desired. Under theseconditions, by holding a nominal pressure of one or two pounds on thewater by means of relief valve 6, practically no loss of water willoccur, and

a maximum head is cre- It will be seen that the direc-- downwardly ofthe coil.

the coil, of the fluid being heated and heaters constructed inaccordance with this invention are, therefore, .highly eillcient in thisregard. It will be understood, ofcourse, that th fluid to be heated inunit 21 may be processed at any desired pressure, it being onlynecessary to construct the coil 20 of materials sufficiently strong towithstand whatever pressure is required.

By keeping the heating unit I. completely immersed in the liquidtransfer medium, the heat generated in the unit is transferred veryrapidly to the liquid, especially since a rapid thermo-syphon flow ismaintained across the heater sur-. faces, and burning out of the metalofth fire tube and ducts is practically eliminated, or .at least greatlyreduced as compared with more conventional heaters. The immersion of theflre tube and ductsin the transfer liquid also permits absorption by thetransfer liquid of maximum quantities of heat generated from thecombustion of a given weight of fuel, thereby further increasing thover-all efliciency of the heating device.

- A particularly useful adaptation of the heating device of thisinvention is its application to the prevention of hydrate formationresulting from the reduction of pressure of high pressure natural gasescontaining some water vapor. This application is coming intoincreasingly greater use due to the increasing production of very highpressure natural gases having initial pressures ranging generally fromabout 1000 lbs/sq. in. to 5000 or more lbs/sq. in. To process such gasesfor various commercial purposes, it is ordinarily necessary to greatlyreduce these high pressures. Since such gases normally contain watervapor in varying amounts, the great reductions in temperatures whichnormally accompany the 'reductions in pressure result in the productionof solid hydrocarbon-water compounds, commonly known as hydrates. Thesetend to gather at various points in the gas conduits and containingvessels, and particularly at the point of expansion of the gas,resulting in ,clogging of the lines and equipment, and are verytroublesome and detrimental to continuously operating processes.

The heater of the present invention may be readily adapted forheatingsuch gases during their expansion to prevent hydrate formation, by aslight modification of th previously described apparatus. Themodification is illustrated particularly in Fig. 6. Gas at highpressures is supplied to coil 28 through connection from a high pressuregas source, such as a well or-a high pressure separator (not shown).Coil 28 will, of

course, be constructed of heavy steel pipe and fittings to withstand thehigh pressures involved. Valve 36 will be a high pressure valve havingan elongated stem 4|, fitted at one end with a handle l3 and extendinginto tube 29 through a stufllng box 42. The stem is of sufllcient lengthto extend well into inlet tube 29 to a point where the tube is immersedin the heat transfer liquid. At thatpoint stem 4| is provided with aneedle valve 44 which cooperates with a conical valve seat 45 throughwhich the high pressure gas is expanded. Expansion of the gas throughvalve seat 45 will, therefore, take place at a point which is within theinterior of tank I and which is subject to heating by contact with thetransfer liquid. This arrangement will permit the transfer liquid toheat the expanding gas, at the point of expansion, to a temperaturesufficiently high to prevent hydrate formation at that point. Of gaswill take place course, expansion of the be heated to increasingly hightemperatures until, at the outlet of the coil, the temperature will bethat desired as a final temperature for the gas.

By this described arrangement for efl'ecting expansion of the gas at theinlet to the heating zone, the minimum temperature produced at thatpoint by the expansion of the gas will greatly ,promote the over-allheat transfer emciency of the heater by providing at the inlet a maximummean temperature difference between the gas to be heated and the heatingmedium.

In connection with the several modifications and applications of thisinvention, it is found that by maintaining a pressure slightly aboveatmospheric pressures on the transfer liquid in the tank, the entranceof air into the tank is eflectively prevented, thereby greatly reducingthe danger ofcorrosion o the metal surfaces of the tank and of theimmersed units by the dissolution of air in the transfer liquid.

From th foregoing, it will be evident that heating, devices, constructedin accordance with this invention, provide many advantages over moreconventional heaters, are comparatively simple in construction, and arehighly efficient for heating a wide variety of fluids.

What we claim and desire to secure by Letters Patent is:

l. A heating apparatus, comprising, an enlarged chamber adapted tocontain a body of a liquid heat transfer medium, a partitioning memberdividing said chamber into separate generally upper and lowercompartments, and means to produce thermo-syphonic circulation of saidmedium between said compartments comprising, a tubular coil positionedin the upper compartment, a heating gas conduit positioned in said lowercompartment, both said coil and said conduit being adapted to besubmerged in said medium, means to supply a high pressure heat-absorbingfluid to said coil, pressure reducing means associated with said coilfor reducing the pressure of said fluid while in passage through saidcoil, means to supply heating fluid to said con duit, and spacedpassageways through said partitioning member providing communicationbetween said compartments.

2. A heating apparatus, comprising, an enlarged chamber adapted tocontain a body of a liquid heat transfer medium, a partitioning memberdividing said chamber into separate generally upper and lowercompartments, and means to produce thermo-syphonic circulation of saidmedium between said compartments comprising, a tubular coil positionedin the upper compartment, a heating gas conduit positioned in said lowercompartment, both said coil and said conduit being adapted to besubmerged in said medium, means to supp y a high pressure heat-absorbingfluid to said coil, pressure reducing means positioned adjacent theinlet of said coil and operative to reduce the pressure of said fluid inthe adjacent inlet portion of said coil, means to supply heating fluidto. said conduit, and spaced passageways through said partitioningmember providing communication between said compartments.

3. A heating apparatus, comprising, an enlarged chamber adapted tocontain a body of a liquid heat transfer medium, a heat insulatingpartitioning member dividing said chamber into separate generally upperand lower compartas the gas proceeds through the coil, it will ments,and means to produce thermo-syphonic circulation of said medium betweensaid compartments comprising, a tubular coil positioned in said uppercompartment, a heating unit positioned in said lower compartment, bothsaid coil and said unit being adapted to be submerged in said medium,said heating unit including a combustion chamber, a flue gas returnconduit and a burner means positioned adjacent the entrance of saidcombustion chamber, means to supply a heat-absorbing fluid to said coil,and spaced passageways through said partitioning member providingcommunication between said compartments.

4. A heating apparatus, comprising, an elongated horizontally positionedchamber adapted to contain a body of a liquid heat transfer medium, athermally non-conductiv partitioning member extending horizontally andlongitudinally of said chamber to divide said chamber into generallyupper and lower compartments, and means to produce thermo-syphoniccirculation of said medium between said compartments comprising,passageways at opposite ends of said partitioning member providingcommunication between said compartments, an elongated tubular coilpositioned in said upper compartment and extending longitudinallytherein from one end of said chamber to a point adjacent one of saidpassageways, an elongated heating element positioned in said lowercompartment and extending longitudinally therein from the opposite endof said chamber to a point adjacent the other of said passageways, meansto supply a heatabsorbing fluid to said coil, and means to supply aheating fluid to said heating element.

5. A heating apparatus, comprising, an elongated horizontally positionedchamber adapted to contain a body of liquid heat transfer medium, athermally non-conductive partitioning member extending longitudinallyand horizontally of said chamber to divide said chamber into separategenerally upper and lower compartments, and means to producethermo-syphonic circulation of said medium between said compartments 7comprising, passageways at opposite ends of said partitioning memberproviding communication between said compartments, an elongated tubularcoil positioned in said upper compartment and extending longitudinallytherein from one end of said chamber to a point adjacent one of saidpassageways, an elongated heating element positioned in said lowercompartment and extending longitudinally therein from the opposite endof said chamber to a point adjacent the other of said chamber to a pointadjacent the other of said passageways, an inlet connection to supply aheat-absorbing fluid to said coil, 8. pressure-reducing valve positionedin said inlet connection and having its discharge orifice within saidcoil, and means to supply a heating fluid to said heating element.

6. A heating apparatus, comprising, an elongated horizontally positionedchamber adapted to contain a body of a liquid heat transfer medium, athermally non-conductive partitioning member extending horizontally andlongitudinally of said chamber to divide said chamber into generallyupper and lower compartments, and means to produce thermo-syphoniccirculation of said medium between said compartments comprising,passageways at asseosa and extending longitudinally therein from one endof said chamber to a point adjacent one of said passageways, a pluralityof transverse baffle members spaced longitudinally along said coil toprovide a plurality of separate pathsacross said coil for said medium,an elongated heating element positioned in said lower compartment andextending longitudinally therein from the opposite end of said chamberto a point adjacent the other of said passageways, means to supply aheat-absorbing fluid to said coil, and means to supp y a heating fluidto said heating element.

'1. A heating apparatus, comprising, an elongated horizontallypositioned chamber adapted to contain a body of a liquid heat transfermedium, a thermally non-conductive partitioning member extendinghorizontally and longitudinally of said chamber to divide said chamberinto generally upper and lower compartments, and means to'producethermo-syphonic circulation of said medium between saidcompartmentscomprising, passageways at opposite ends of said partitioning memberproviding communication between said compartments, an elongated tubularcoil positioned in said upper compartment and extending longitudinallytherein from one end of said chamber to a point adjacent one of saidpassageways, a plurality of transverse baffle members spacedlongitudinally along said coil to provide a plurality of separate pathsacross said coil for said medium, an elongated heating elementpositioned in said lower compartment and extending longitudinallytherein from the opposite .end of said chamber to a point adiacent theother of said passageways, said heating element including an elongatedcombustion tube closed at its inner end, rpair of spaced parallel fluegas return conduits communicating with opposite sides of said combustiontube adjacent its inner end and returning to the exterior of saidopposite end of said chamber, a smoke stack communicating with the outerends of said return conduits, burner means positioned in the outer endportion of said combustion tube for supplying hot gases of combustion tosaid heating element, and means to supply a heatabsorbing fluid to saidtubular coil.

8. A heating apparatus, comprising, a'heating chamber containing a bodyof a liquid heat transfer medium, a partitioning member dividing saidchambers into separate generally upper and lower compartments, aheat-supply element positioned in the lower compartment and aheatabsorbing element disposed in the upper compartment, both saidelements being submerged in said medium, spaced passageways through saidpartitioning member to provide communication between said compartments,means to supply a heating fluid to said heat-supply element, means tosupply high pressure gas to said heatabsorbing element to therebyproduce thermosyphonic circulation of said medium between saidcompartments, means arranged in said heat-absorbing element for reducingthe pressure of said gas in an inlet portion thereof within said chamberfarthest removed from the inlet portion of said heat supp yin element tothereby produce a -maximum mean temperature difference between saidinlet portion of the heat-absorbing element and said medium.

9. A heating apparatus including, a heating chamber containing a body ofliquid heat-trap for medium, a heat-supplying element and aheat-absorbing conductor both disposed in said fill 1y flow from thelower chamber in spaced relation to each other, said element and saidconductor being submerged in said medium, means to s pp y a heatingfluid to said heat-supplying element. means to supply and provide acooled high pressure gas flowing through the conductor to therebyproduce thermo-syphonic circulation of said heat-transfer medium betweensaid element and said conductor, and means for diverting thethermo-syphonic circulation flow to produce a maximum heat transferbetween the conductor and said medium. I

10. A heating apparatus as set forth in claim 9,

and a heat-insulating partition disposed between the heat-supply elementand the conductor.

11. A heating apparatus including, a chamber containing a body of liquidheat-transfer medium, a burner element and a heat-absorbing conductorboth having portions disposed in said chamber and submerged in saidmedium in spaced relation to each other, means to supply a high pressuregas to said conductor for circulation therethrough, and means to reducethe pressure of said gas entering said conductor thereby cooling saidgas and producing thermo-syphonic circulation of said medium betweensaid element and said conductor.

12. A heating apparatus as set forth in claim 11, and means in thechamber for diverting the thermo-syphonic flow across the conductor toproduce a maximum heat exchang between the heat-transfer medium and thegas- 13. A heating apparatus as set forth in claim 11, and aheat-insulating element spaced from and extending between the burnerelement and the conductor to induce thermo-syphonic circulation of saidmedium.

14. A heating apparatus including, an elongate substantially horizontaltank containing a body of heat-transfer medium, a partition within thetank extending medially and longitudinally thereof and dividing saidtank into generally upper and lower longitudinal compartments, acirculating heat-transfer fluid-conductor connected to one end of thetank and disposed longitudinally of the partition in the uppercompartment of the tank, a heating element connected to the opposite endof the tank and disposed in the lower compartment of the tank, thefluid-conductor and the heating element being fully immersed in theheat-transfer medium. the opposite ends of the partition terminatingshort of the ends of the tank to provide opposed circulating flowbetweenthecompartmentstocause the heat-transfer medium tothermo-syphonicalcompartment to the upper compartment and longitudinallyof the fluidconductor and the partition and to return to the lowercompartment. Y

i5. Aheating apparatusassetforthinclaim 14, wherein the passages at theends of the partition are provided with restrictions to cause theheat-transfer medium to flow from the lower compartment into the uppercompartment at an increased velocity.

16. Aheatingapparatusas setforthin-claim 14andmeansintheuppercompartmenttodivert the flow of the heat-transfermedium across the conductor to obtain maximum heat exchange.

i'LAheatingapps-rltusassetforthinciaih: it in which the heating elementextends longitudinally in saidlower t.

JAY P. WALKER. m 0. GLASGOW.

